Many computer systems include an input device that allows physical actions of a user to be translated into manipulations of a graphical user interface of the computer system. For example, most desktop computers are configured with pointing device such as a mouse. When the mouse is moved relative to a fixed surface, movement of an on-screen cursor occurs in a direction and at a speed that corresponds to the physical movement of the mouse.
While the basic mouse has enjoyed widespread adoption as an input device for desktop computers, it can be less practical for use with portable computer systems or systems that are situated in a cluttered work environment. A number of pointing devices have been developed for such systems, however each suffers from inherent drawbacks.
A first type of pointing device involves a small joystick. The joystick includes a finger pad coupled to a small shaft that pivots relative to a fulcrum point. The direction in which the joystick is angled relative to the fulcrum point is used to determine a direction to move the on-screen cursor, and a force applied to the joystick is used to determine a speed at which to move the on-screen cursor. One advantage to this type of pointing device is that it can be positioned in proximity to a keyboard (e.g., in the center of a keyboard as in the case of a laptop computer). This allows a user to switch between using the keyboard and using the pointing device without having to move their hands from a “home” position. The moving parts involved in this type of pointing device are susceptible to failure however, particularly when a user applies excessive input force. In addition, dust, dirt, or oils can easily contaminate or otherwise disrupt the delicate parts of the pointing device. Further still, repeated application of excessive force to the pointing device to obtain fast cursor movement can lead to user pain and repetitive stress injuries. This type of pointing device can also suffer from cursor drift, and a user can find it difficult to reliably apply the correct amount of force.
U.S. Pat. No. 5,764,219 to Rutledge et al. discloses exemplary signal processing that can be used with pointing devices of the first type. Input force applied to the joystick is related to a velocity of a cursor on a video screen according to a transfer function. The transfer function, shown in FIG. 2 of the Rutledge patent, has a dead band between force thresholds F0 and F1, a low plateau between force thresholds F2 and F3, a parabolic-sigmoid between force thresholds F3 and F4, and a high plateau between force thresholds F4 and F5.
A second type of pointing device involves an optical scanner that reads the swipe of a user's finger. While this type of pointing device generally does not have moving parts, it requires several swipe actions by the user when moving a cursor for a long distance, which is inefficient and can cause user discomfort, fatigue, or annoyance. This type of pointing device also usually requires movement of the user's hands from the home position, which is undesirable.
U.S. Pat. No. 6,552,713 to Van Brocklin et al. discloses an exemplary pointing device of the second type. The Van Brocklin device uses a transparent curved surface and an optical sensor to detect movement of a user's finger. The optical sensor captures successive images of the curved surface and calculates the change in position of a user's finger between the successive images. This change in position is related to a time scale and used to generate direction and velocity data for moving a cursor. The device of Van Brocklin is thus analogous to the second type of pointing device described above, in that it relies on motion of a user's finger relative to a fixed surface to determine cursor speed and direction.
Japanese Publication No. JP2003-216321 to Kato discloses a pointing device of the second type that is very similar to the device disclosed in Van Brocklin. A dome-shaped cover is provided over an image pickup element which captures a video signal of a user's finger moving across the dome-shaped cover. This movement detection is used to control movement of a cursor on a display.
U.S. Pat. No. 6,057,540 to Gordon et al. discloses yet another pointing device of the second type in which a transparent stud is provided over an image sensor. Movement of a user's finger across a top surface of the stud is detected and translated into motion of a cursor.
A third type of pointing device involves a jog ball mounted within a recess and configured to rotate first and second orthogonal rollers when the ball is manipulated by a user. Like the joystick type pointing devices described above, this type of device includes moving parts and is susceptible to contamination from dirt or dust. Pointing devices of the third type can also be broken easily when excessive operating force is applied.
In view of these and other shortcomings, a need exists for improved pointing devices.
Each of the patents and publications discussed above are incorporated herein by reference in their entireties.